1. Field of Invention
The present invention relates to grinding optical lenses, and is particularly related to improvements in grinding pads used for grinding optical and opthalmic lenses. More specifically, this invention is concerned with an abrasive pad which is uniquely suitable for grinding optical and opthalmic lenses without the aid of an abrasive slurry during the grinding operation.
2. Description of the Prior Art
Grinding of optical and opthalmic lenses are well known in the art, and indeed there are several patents and publications which essentially describe the present day methods of grinding such lenses. Basically these methods comprise grinding a lens blank to a precise and predetermined curvature in order to impart the required optical characteristics to the finished lens. A typical prior art method, for example, is described in U.S. Pat. No. 3,699,721 issued on Oct. 24, 1972. According to this patent the grinding operation is performed by the use of a cast iron tool with a lapping surface having a curvature which corresponds precisely to the desired curvature to be impressed upon the lens blank. An oscillatory motion, or a combination of oscillatory and rotary motions is imparted between the lens blank and the lapping surface while a stream of an abrasive slurry is deposited over the lapping surface in order to grind the lens blank.
Other patents disclose grinding optical and opthalmic lenses using essentially the same procedure as described in the aforementioned patent, but employing variously designed pads adapted to conform to the curvature of the surface of a working tool. These pads which are interposed between the lens blank and the surface of the working tool provide a surface for a stream of abrasive slurry which is independently deposited on the tool surface. See, e.g., U.S. Pat. Nos. 2,886,923 and 3,144,737.
The principal disadvantage of the pads which have heretofore been used during the grinding of optical and opthalmic lenses is that notwithstanding their use, an abrasive slurry must be employed in order to effectively grind the lens blanks. The prior art pads generally consist of metallic foils of various configurations designed to conform to the curvature of the surface of the working tool and are by themselves ineffective for grinding the lens blanks, unless an independent source of an abrasive medium is employed. The use of abrasive slurry, however, for grinding of these lens blanks is both a costly and cumbersome operation. Accordingly, there is a need for a grinding pad for use in grinding lens blanks without the necessity for concommitant use of an abrasive slurry.